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A New Genus and Species of Blind Sleeper (Teleostei: Eleotridae) from Oaxaca,
Mexico: First Obligate Cave Gobiiform in the Western Hemisphere
Author(s): Stephen J. Walsh and Prosanta Chakrabarty
Source: Copeia, 104(2):506-517.
Published By: The American Society of Ichthyologists and Herpetologists
DOI: http://dx.doi.org/10.1643/CI-15-275
URL: http://www.bioone.org/doi/full/10.1643/CI-15-275
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A New Genus and Species of Blind Sleeper (Teleostei: Eleotridae) from
Oaxaca, Mexico: First Obligate Cave Gobiiform in the Western Hemisphere
Stephen J. Walsh
1
and Prosanta Chakrabarty
2
Caecieleotris morrisi, new genus and species of sleeper (family Eleotridae), is described from a submerged freshwater
cave in a karst region of the northern portion of the State of Oaxaca, Mexico, R´
ıo Papaloapan drainage, Gulf of Mexico
basin. The new species represents the first cave-adapted sleeper known from the Western Hemisphere and is one of only
13 stygobitic gobiiforms known worldwide, with all others limited in distribution to the Indo-Pacific region. The new
taxon represents a third independent evolution of a hypogean lifestyle in sleepers, the others being two species of
Oxyeleotris (O.caeca and O.colasi) from New Guinea and a single species, Bostrychus microphthalmus, from Sulawesi.
Caecieleotris morrisi, new species, is distinguished from epigean eleotrids of the Western Atlantic in lacking functional
eyes and body pigmentation, as well as having other troglomorphic features. It shares convergent aspects of
morphology with cave-dwelling species of Oxyeleotris and B.microphthalmus but differs from those taxa in lacking
cephalic pores and head squamation, among other characters. Description of C.morrisi, new species, brings the total
number of eleotrid species known from Mexico to 12. Seven of these, including the new species, occur on the Atlantic
Slope.
Caecieleotris morrisi,g
´
enero y especie nuevos de dormil ´
on (familia Eleotridae), se describe de una cueva sumergida de
agua dulce en una regi´
on ka
´rstica del Estado de Oaxaca, M´
exico, cuenca del r´
ıo Papaloapan, vertiente del Golfo de
M´
exico. La nueva especie representa el primer ele ´
otrido cavern´
ıcola del Hemisferio Occidental y es uno de los pocos
gobiiform estigobiontes (s ´
olo 13) conocidos mundialmente, todos los dema
´s de distribuci ´
on limitada a la regi ´
on del
Indo-Pac´
ıfico. El nuevo tax ´
on representa la tercera evoluci ´
on independiente del modo de vida hip´
ogeo en los
dormilones; los otros son dos especies de Oxyeleotris (O.caeca yO.colasi) de Nueva Guinea y una sola especie, Bostrychus
microphthalmus, de las islas C´
elebes (Sulawesi). Caecieleotris morrisi se distingue de los ele ´
otridos ep´
ıgeos del Atla
´ntico
occidental por la ausencia de ojos funcionales y de pigmentaci´
on en el cuerpo, as´
ı como por otras caracter´
ısticas
troglom ´
orficas. Comparte aspectos morfol ´
ogicos convergentes con especies cavern´
ıcolas de Oxyeleotris yB.
microphthalmus, pero difiere de ´
estas por la falta de poros cefa
´licos y escamaci ´
on en la cabeza, entre otros caracteres.
La descripci´
on de C.morrisi lleva el n´
umero total de ele ´
otridos conocidos de M´
exico a doce. Siete de estos, incluyendo la
nueva especie, ocurre en drenajes del Atla
´ntico.
CAVEFISHES have long been of keen interest to
biologists interested in evolutionary forces that drive
convergence of form and function in these uniquely
derived organisms (e.g., Eigenmann, 1909; Poulson, 1963,
2001; Romero, 2001; Trajano et al., 2010). The most
generalized and ubiquitous morphological features of trog-
lomorphy, morphological features associated with subterra-
nean life—loss or reduction of eyes, depigmentation, and the
elaboration of non-optic sensory systems—are well docu-
mented for numerous species in diverse lineages. Extensive
study of some taxa (e.g., Astyanax, Amblyopsidae) has led to
their status as model organisms for many lines of investiga-
tion (e.g., Wilkens, 1988; Jeffery, 2001, 2009; Niemiller and
Poulson, 2010; Protas and Jeffery, 2012; Soares and Niemiller,
2013), and the diversity of hypogean fishes and many aspects
of their biology have been reviewed in a number of notable
compilations (Thines, 1969; Weber et al., 1998; Weber, 2000;
Romero, 2001; Romero and Poulson, 2001; Wilkens, 2005;
Proudlove, 2006, 2010). In recent years there has been a surge
in new discoveries and taxonomic descriptions of cavefishes
as scientific exploration of subterranean habitats has in-
creased, including many previously undocumented or unex-
plored systems (Pouyaud et al., 2012; Sparks and
Chakrabarty, 2012; Larson et al., 2013; Chakrabarty et al.,
2014), and as cryptic diversity is increasingly revealed
through molecular work (Niemiller et al., 2012). This is
particularly true of regions in the world rich in karst
topography and where previous biospeleological exploration
has only been comparatively recent, such as Southeast Asia
(especially China), the Neotropics, and Madagascar.
On a global scale over 300 fish species have been reported
to live or occur in caves and other subterranean habitats
(Soares and Niemiller, 2013), about half of which are
occasional or peripheral in occurrence. Time since divergence
from surface-dwelling sighted ancestors is manifested among
hypogean species by a gradation of morphological, physio-
logical, behavioral, neurological, and other features. A
limited number of those species reported from subterranean
habitats are considered to be obligate cave species, i.e., living
entirely in hypogean habitats, having obvious morphological
adaptations to a cavernicolous life style and typically
considered as troglobites, or, in terminology appropriately
applied to aquatic taxa, stygobites. In contrast, troglophiles,
trogloxenes, and accidentals are species that lack extreme
morphological specialization, and, with the exception of
some populations of the former, do not typically complete
their life cycles in caves (see Discussion and references in
Franz et al., 1994). About 170 species from 22 families and
ten orders of stygobitic cavefishes are currently documented
(Proudlove, 2010), whereas in the early 1990s only about 50
species were known (Allen, 1996). Each of the 22 families
represents at least one evolutionary occurrence in cave
habitats, and most of the families have several independent
lineages. Most stygobitic fish taxa appear to have been
derived from freshwater ancestors. Thus, apart from their
obvious interest to scientists in many disciplines, including
1
U.S. Geological Survey, 7920 NW 71
st
Street, Gainesville, Florida 32653; Email: swalsh@usgs.gov. Send reprint requests to this address.
2
Museum of Natural Science, Ichthyology Section, 119 Foster Hall, Department of Biological Sciences, Louisiana State University, Baton Rouge,
Louisiana 70803; Email: prosanta@lsu.edu.
Submitted: 1 April 2015. Accepted: 24 September 2015. Associate Editor: T. J. Near.
Ó2016 by the American Society of Ichthyologists and Herpetologists DOI: 10.1643/CI-15-275 Published online: 14 June 2016
Copeia 104, No. 2, 2016, 506–517
evolutionary biology, systematics, physiology, genetics, and
functional morphology, cave-dwelling organisms also pro-
vide excellent subjects for examining ancient biogeographic
disjunctions (Chakrabarty et al., 2012).
The order Gobiiformes, Percomorphacea (Betancur-R. et
al., 2013; Thacker et al., 2015), is a widespread and
morphologically diverse group (.2,200 species) that includes
several blind, cave-adapted taxa. Previously described stygo-
bitic gobiiforms are known exclusively from the Indo-Pacific
region: Japan, Philippines, Indonesia, Sulawesi, Madagascar,
Australia, and Papua New Guinea, with an unconfirmed
species reported from the Micronesian island of Guam (Table
1). Nested within the gobiiforms are the sleepers, family
Eleotridae, found worldwide throughout tropical and sub-
tropical regions and primarily distributed in nearshore
marine, brackish, and fresh waters. Three species of cave
sleepers have been previously described, and an additional
five species of the closely related family Milyeringidae are
known. Herein, we describe the first species of stygobitic
eleotrid known from the Western Hemisphere, a freshwater
taxon from the State of Oaxaca, Mexico, and place it in its
own genus, at present having no known affinity to other
extant hypogean or epigean eleotrids.
MATERIALS AND METHODS
Measurements and meristic counts were taken following the
general methods of Hubbs and Lagler (2004), with slight
modifications and additions following Allen (1996), Pouyaud
et al. (2012), Sparks and Chakrabarty (2012), and Larson et al.
(2013) except as noted. Meristic counts and morphometric
measurements were taken on the left side except where
distortion or damage of a specimen required use of the right
side for an individual count or distance. Point-to-point,
straight-distance measurements were recorded to the nearest
0.1 mm using dial calipers or, in the case of short distances
and small specimens, using an ocular micrometer fitted to a
dissecting microscope calibrated with a stage micrometer.
Pre-fin lengths were measured from the tip of the protruded
lower lip to the base of each anterior fin ray or spine, or, in
the case of the pectoral fin, to the anterior base of the
expanded fleshy pad at the base of the fin. Head length (HL,
in mm) was measured from the tip of the lower lip to the
upper attachment of the opercular membrane. Measure-
ments are expressed as a percentage of standard length (SL, in
mm) or HL. All fin rays and spines were counted as separate
elements, including the last two elements of the second
dorsal and anal fins, where it was difficult to discern whether
articulation was on a single or separate pterygiophore, from
either radiographs or substage light transmission with a
dissecting microscope of whole specimens. Vertebral counts
were obtained from radiographs, are reported as total, and
exclude the ural centrum. Principal (segmented) caudal rays
included all rays directly articulating with the terminal edge
of the hypural plate, as upper and lower on either side of the
gap between the two parts of the hypural. Procurrent rays
included all other unsegmented rays in each lobe; however,
caudal fins were generally frayed and segmentation was
difficult to discern, so recorded counts are provisional. A
single specimen of the type series (UF 101173; 28.2 mm SL)
was cleared and stained (CS) following the procedure of
Potthoff (1984) to confirm anatomical details. Neither the CS
specimen or radiographs permitted detailed study of osteol-
ogy. Institutional abbreviations follow Sabaj P´
erez (2014).
Table 1. Currently recognized stygobitic gobioid fish species of the world associated with freshwater, brackish, and marine (anchialine cave)
habitats, excluding troglomorphic species with convergent morphology but associated with non-subterranean habitats (e.g., burrows, reefs,
commensal species, and deep river channels; see Proudlove, 2006:appendix 3 for partial list, excluding deep-sea taxa).
Family/Subfamily Species Distribution Type specimens
Eleotridae
a
Bostrychus microphthalmus Sulawesi holotype: MZB 5942; paratypes: AMS I.43460-001(2);
CMK 7241(2); MNHN 2004-3089; MZB 5943
Caecieleotris morrisi, new species Mexico holotype: CNPE-IBUNAM 19073; paratypes UF 101173
(9); LSUMZ 17726(1)
Oxyeleotris caeca Papua New Guinea holotype: WAM P.31011.001
Oxyeleotris colasi West Papua,
Indonesia
holotype: MZB 20031; paratypes: MZB 20032(4);
MNHN 2010-0034(4)
Milyeringidae
b
Milyeringa justitia Australia (Barrow
Island)
holotype: WAM P.33166-001; paratypes: WAM
P.33167-001(1); WAM P.33135-001(1); WAM
P.33137-001(1); WAM P.33169-001(1)
Milyeringa veritas Australia holotype: WAM P.2913-001
Typhleotris madagascariensis Madagascar lectotype: MNHN 1933-0060
Typhleotris mararybe Madagascar holotype: AMNH 245601; paratype: AMNH 245602
Typhleotris pauliani Madagascar holotype: MNHN 1960-0258; paratypes: MNHN 1960-
0259(6)
Gobiidae
(Gobiinae)
Glossogobius ankaranensis Madagascar holotype: BMNH 1944.12.1.1; paratypes: BMNH
1994.12.1.2(1)
Gobiidae
(Gobionellinae)
Caecogobius cryptophthalmus Philippines (Samar
Island)
holotype: MSNVR 1262; paratypes: MSNVR 1262a (1,
partially dissected), 1262b (1, stained, partially
dissected); ZSM 27189 (stained)
Luciogobius albus Japan syntypes: ZUMT 25693(1), 25762(1)
Luciogobius pallidus Japan syntypes: ZUMT 11607(1), 16147(1), 26342(1)
a
An undescribed species provisionally assigned to Eleotris has been reported from Guam, Micronesia (Proudlove, 2010).
b
Higher-group classification debated based on morphological and molecular analyses; some authors place within the Eleotridae (e.g., Larson
et al., 2013; Eschmeyer and Fong, 2016). We recognize the family following Chakrabarty (2010), Chakrabarty et al. (2012), and Tornabene
et al. (2013).
Walsh and Chakrabarty—New cavefish from Mexico 507
Caecieleotris, new genus
urn:lsid:zoobank.org:act:B0626A75-66BC-4F7E-A427-
B092870D954F
Type species.—Caecieleotris morrisi, new species, by monotypy
and original designation.
Diagnosis.—Caecieleotris is a blind, freshwater, hypogean
eleotrid that is distinguished from the majority of other
sleepers, and all epigean forms in the Western Atlantic, by
the absence of eyes and pigmentation. Caecieleotris is
provisionally placed in the Gobiiformes, family Eleotridae,
on the basis of a limited number of characters that it shares
with other members of the family as currently recognized,
e.g., having a mode of six branchiostegals, pelvic fins
separated at the base, and procurrent cartilages of the caudal
fin elongated posteriorly and extended over the epurals (see
Discussion). Caecieleotris differs from the cave-dwelling
Bostrychus microphthalmus of Sulawesi in the absence of eyes
(versus present, minute, covered by skin), complete lack of
pigmentation (versus body pale, few melanophores on
dorsum), lack of scales on operculum and side of head
(versus present), lower lateral scale count (32 versus 102),
fewer transverse scale rows on midside of body (6 versus
31), and absence of pores associated with the cephalic
lateralis system (versus present). Caecieleotris can be distin-
guished from the blind species of Oxyeleotris of Indonesia (O.
colasi) and Papua New Guinea (O. caeca) in lacking sensory
pores on the head associated with the cephalic lateralis
system (versus cephalic sensory pores present, although
reduced in comparison to other gobiiform fishes). Caecieleo-
tris can be distinguished from the cave species of Typhleotris
from Madagascar (T. madagascariensis,T. mararybe, and T.
pauliani) in having the head asquamate (versus scales
extending anteriorly onto the head), squamation absent on
the venter (versus fully scaled on the belly as well as laterally
below the pectoral fin), scales embedded (especially on
anterior half of body) and hard to discern (versus in
prominent rows on the surface of the body and head).
Species of the western Australian cave-dwelling Milyeringa
have elements of the first dorsal fin reduced (spines II–IV; M.
veritas) to absent (M. justitia), versus V–VI in Caecieleotris.
Species of Milyeringa also have 4–5 total lepidotrichia (first
unsegmented) in the pelvic fin versus six in Caecieleotris.
Etymology.—Caeci from the Latin meaning blind, and eleotris,
referring to the common and widespread type genus of
Eleotridae.
Remarks.—Discovery of C. morrisi, new species, represents
only the fourth known hypogean species of Eleotridae, and it
appears to be an independent evolutionary derivation given
the extremely disjunct geography between it and other cave-
dwelling eleotrids. Moreover, it differs from extant epigean
eleotrids in the Western Atlantic and Eastern Pacific (i.e.,
species of Dormitator,Eleotris,Erotelis,Gobiomorus,and
Guavina) by its pronounced troglomorphic features. The
separate pelvic fins and general body shape are characteristic
of species of Eleotridae and readily distinguish C. morrisi, new
species, from the many genera and species of Western
Atlantic gobies (see Murdy and Hoese, 2002) that occur in
proximity to its range, most of which are marine in
distribution. In addition to the independently derived
Indo-Pacific cave eleotrids, the eleotrid-like Milyeringidae
also includes cave-inhabiting species of the Malagasy and
Australian genera Typhleotris and Milyeringa, but none of
these taxa are considered to be related to C. morrisi, new
species. All of these cave taxa share certain morphological
features but also vary in the degree to which they exhibit
extreme troglomorphic features (see Discussion).
Caecieleotris morrisi,new species
urn:lsid:zoobank.org:act:193B8DF5-31BD-4BE6-AAD5-
34A6DF872681
Oaxaca Cave Sleeper, Guavina Cueva de Oaxaca
Figures 1, 2, 3; Table 2
Holotype.—CNPE-IBUNAM 19073 (ex. UF 101173), 34.1 mm
SL, Mexico, Oaxaca State, submerged cave at the bottom of
Presa Miguel Alema
´n reservoir, approximately
18811022.58 00 N, 96836056.02 00 W, 16 April 1995, T. L. Morris.
Paratypes.—LSUMZ 17726 (ex UF 101173), 1, 28.0 mm SL;
UF 101173, 9, 11.6–31.6 mm SL (1 CS, 28.2 mm SL); UMMZ
231174, 2, 19.3–29.9 mm SL. Same locality and date as the
holotype.
Diagnosis.—Species diagnosis is that of the monotypic genus,
with character states of Caecieleotris as stated above.
Description.—Selected proportional measurements presented
in Table 2. A diminutive, anophthalmic, unpigmented
eleotrid. Size range of type specimens 11.6–34.1 mm SL.
Body slender, relatively elongate, laterally compressed, body
depth at pelvic-fin origin 14.2–18.6% SL (Fig. 1A). Body
width at pectoral-fin origin 11.6–17.4% SL. Head broad and
moderately depressed, shovel-shaped, head width 54.1–
68.2% HL. Snout prominently upturned. Dorsal profile of
head straight to weakly concave. Ventral profile of head
weakly convex. Dorsal and ventral profiles of body posterior
to pectoral fins gradually tapered, nearly symmetrical except
for position of median fins, body depth only slightly reduced
from pectoral-fin insertion to anal-fin origin. Caudal pedun-
cle relatively shallow (depth 7.4–8.4% SL) and narrow (width
2.9–5.4% SL). Deep fleshy groove on ventral side of body
from pectoral-fin insertion to anal-fin origin, with a keel-like
midventral flap of skin, possibly representing artifact of
shrinkage following preservation or presence of little or no
food in the gut of individuals when preserved.
Meristic characters exclude data for the two smallest,
presumably juvenile, paratypes (UF 101173; 11.6–11.9 mm
SL) and include only partial data for two other paratypes
(UMMZ 231174). Values for holotype indicated by asterisk,
number of specimens parenthetically as follows. First dorsal-
fin elements modally VI: V (5), VI* (6); spines thin, flexible.
Second dorsal-fin elements modally I,7: I,7* (6), I,8 (5). Anal-
fin ray elements modally I,8: I,6 (1), I,7 (2), I,8* (6), I,9 (1),
I,10 (1). Pelvic-fin elements I,5* (11). Spines in second dorsal,
anal, and pelvic fins feeble, thin, flexible. Pectoral-fin rays
modally 14: 13 (4), 14 (6), 15* (1). Upper principal
(segmented) caudal-fin rays modally 6: 5 (1), 6* (7), 7 (3).
Lower principal caudal-fin rays modally 6: 5* (4), 6 (5), 7 (2).
Upper procurrent caudal-fin rays modally 8: 5 (1), 6 (3), 7 (2),
8* (5). Branchiostegals modally 6: 4 (1), 5 (1), 6* (9). Scales in
lateral series modally 27: 25 (2), 26 (1), 27 (3), 28* (1), 31 (2),
32 (1). Scales on body cycloid, large (5–6 transverse scales on
midside of body), imbricate, thin, tightly appressed to body.
Circumferential caudal peduncle scales modally 10: 10* (6),
508 Copeia 104, No. 2, 2016
Fig. 1. Holotype of Caecieleotris morrisi, CNPE-IBUNAM 19073, 34.1 mm SL, sex undetermined, in lateral (A), dorsal (B), and ventral (C) views.
Walsh and Chakrabarty—New cavefish from Mexico 509
11 (4). Total vertebrae modally 24: 24* (6), 25 (3). Rib pairs
modally 6: 6 (4), 8* (2).
Head large, its length 29.2–42.5% SL. Dorsum of snout at
midline forming a small raised bump, extending posteriorly a
short distance along midline as a weakly ossified ridge. Snout
broadly crescentic in dorsal view (Fig. 1B). Mouth large,
superior, length of both jaws about one-third HL; mouth
distinctly upturned, midline of lower jaw projecting anterior
to midline of upper jaw. Posterior edges of jaws curved gently
inward in ventral view (Fig. 1C). Lips relatively thin,
prominent groove between upper lip and anterodorsal part
of head, frenum present at midline. Basihyal reaching to
approximately midway between tip of snout and rear margin
of jaw. Teeth in upper and lower jaw conical, slender, sharp,
uniform in size, slightly recurved inward, in 1–3 irregular
rows. Gill rakers short, blunt, denticulate at terminal end; gill
filaments also short, about 3–4 times length of rakers. Nares
large and prominent, anterior naris a broad tube extending
above upper lip and angled forward about 458from sagittal
plane of head, with thin fleshy flap surrounding oval
opening. Posterior naris a large, oval to circular, dorsal-
oriented opening lacking marginal flap. Nasal rosette and
broad tubular connection between anterior and posterior
nares readily visible through unpigmented skin. Brain visible
beneath skin on top of head, detailed structure not readily
visible eternally, but olfactory lobes, cerebellum, and hind-
brain evident; optic lobes presumed reduced. Olfactory nerve
well developed. Narrow posterior process of mesethmoid and
lateral ethmoid articulating with long, closely apposed
frontals, together forming a narrow median keel-like ossifi-
Fig. 2. Neurocranium in dorsal view of (A) Caecieleotris morrisi (UF 101173, paratype) and (B) Eleotris perniger (UF 27603). Abbreviations: e, eye; f,
frontal; o, anophthalmic orbital region, illustrating thin, rod-like ossification in (A) in comparison to broad, laminar shelf in (B). Scale bars ¼5mm.
510 Copeia 104, No. 2, 2016
cation connecting the upper jaw bones with the rear of the
skull (Fig. 2A), much thinner than in Eleotris (Fig. 2B). Large
oval foramen on dorsum of head in anophthalmic orbital
region (Fig. 2A), on each side of longitudinal midline, formed
in unossified area surrounded by jaw apparatus anteriorly,
frontals medially, suspensorium posteriorly and ventrolater-
ally, overlain by thin opaque yellow musculature and
integument. No eyes visible externally in most specimens,
but some individuals with a minute spherical black lens
located on either side dorsally just below the epidermis,
slightly medial to point midway between side of head and
center of frontal, at a longitudinal distance of about one-
third from tip of the snout to posterior margin of opercle.
Opercular openings large, thin opercular membranes nearly
separate, only narrowly joined anteroventrally to isthmus.
Posteriorly, opercular membrane attached to body antero-
dorsal to pectoral-fin origin. Branchiostegals acicular, flexi-
ble; anterior 1–2 shortest, posterior-most 3–4 longer, gently
curved dorsolaterally.
Lateral line and cephalic pores absent. Head and body with
profuse distribution of sensory papillae in discrete vertical,
transverse, horizontal, and oblique rows. The head papillae
pattern is essentially the transverse type following the
nomenclature of Hoese (1983), but it is unknown if
individual lines of papillae are homologous with numbered
series as described for many other gobiiforms. The following
description is based on a specimen illustrated in Figure 3 and
the holotype (Fig. 1). Sensory papillae system forming
marked relief on dorsolateral aspect of snout and anterior
portion of head, with rows of papillae developed on
prominent fleshy ridges; 3–5 ridges in preorbital region with
papillae elevated on each ridge in a semicircular pattern from
the dorsolateral edge of the head extending around to the
ventrolateral aspect of the chin (Fig. 3A), with an additional
dorso-ventral oriented ridge of papillae in an approximately
sagittal plane nearly equal to or just behind the posterior
margin of the brain (Fig. 3B). Top of snout with a short
longitudinal series of papillae on each side extending from a
plane just in front of the anterior naris to a plane
approaching the rear margin of the posterior naris, and
another short row of papillae distributed laterally and
obliquely from each longitudinal series toward the posterior
naris. A parallel, oblique row of papillae posterior to the
latter, extending from the mid-dorsal to lateral preorbital
region of the head. Three irregular horizontal series of
papillae on the ventrolateral side of the head, the top two
broken, the lower continuous from the posterior margin of
the jaw to above the origin of the preopercle and posterior-
most branchiostegals; the uppermost of these may corre-
spond to the upper horizontal line (LTU) and the lower to the
lower horizontal line (LTB) as described by Hoese (1983). Five
vertical rows of papillae on the ventrolateral side of the head
distributed from posterior edge of the jaw to anterior edge of
the opercle, apparently corresponding to vertical transverse
lines (VT) of Hoese (1983). Lateral margin of opercle with a
semicircular pattern of papillae in a continuous dorsolateral,
vertical, and ventrolateral row. Posterior half of top of head
with single longitudinal row and irregular, transverse or
obliquely directed papillae distributed mid-medially, postero-
lateral to brain, and dorsally above each opercle. Preopercular
mandibular series consisting of multiple lines of transverse
papillae medial to longitudinal line extending from near
anterior end of lower jaw to lateral opercular margin (Fig.
3C). Two dorsolateral rows of papillae, one above and the
other just posterior to base of pectoral fin. Single longitudinal
row of papillae on each side of middorsal ridge above and just
posterior to base of pectoral fin. About five vertical to
transverse rows of papillae extending from midlateral region
of each side to ventromedial region of abdomen distributed
approximately equally between pectoral-fin insertion and
urogenital papilla. Additional irregularly spaced vertical rows
of papillae distributed along sides of body from plane passing
through second dorsal and anal fins to caudal peduncle.
Fig. 3. Pattern of sensory head papillae series on head of Caecieleotris
morrisi, drawn from composite of UF 101173 (31.6 mm SL, paratype)
and CNPE-IBUNAM 19073 (34.1 mm SL, holotype) in lateral (A), dorsal
(B), and ventral (C) views. Dorsal fin omitted from (B). Scale bar ¼5
mm.
Walsh and Chakrabarty—New cavefish from Mexico 511
First dorsal-fin origin anterior to midpoint of body and
vertical through tip of adducted pelvic rays, pre-spinous-
dorsal fin length 42.7–50.0% SL, base of fin 6.7–13.4% SL.
Origin of second dorsal fin about equal with or slightly
posterior to vertical plane passing through urogenital papilla,
slightly anterior to origin of anal fin. Base of second dorsal fin
7.4–18.2% SL, longer than that of spinous dorsal but less
than anal-fin base length. Both second dorsal and anal fins
high, sinuous, broadly rounded, middle branched rays
longest. Anal fin long, base length 11.4–19.8% SL, origin
slightly posterior to urogenital papilla, insertion slightly
posterior to that of second dorsal fin. Caudal fin pointed to
lanceolate, middle rays longest (sometimes considerably
longer than others), terminal ends of rays frayed in some
specimens (see Fig. 1A; in comparison, species of Dormitator
have a broadly rounded fin, and species of Eleotris,Gobiomo-
rus, and Guavina have a semi-truncate to rounded fin). Bases
of pelvic fins apposed but fins separate (as in other eleotrids,
compared to fused in most gobiids), jugular, anterior to plane
passing through origin of pectoral-fin rays but about equal
with anterior edge of thick anteromedial pectoral-fin mus-
culature, posterior to symphysis of opercular membranes.
Pelvic fin relatively long and ribbon-like, pointed, middle to
posterior branched rays longest, tip of appressed fin not
reaching to genital papilla. Pectoral-fin base obliquely
vertical, origin (dorsal edge) slightly posterior to insertion
(ventral edge), basal portion surrounding proximal radials
projecting from body as fleshy appendage. Pectoral fins
elongate and produced with filamentous rays, most pro-
nounced in larger individuals, middle branched rays longest,
tips of appressed fins reaching well posterior to anal-fin
origin.
Coloration in preservative.—Head and body without pigmen-
tation, uniformly white to yellowish and opaque in appear-
ance. Fins translucent or transparent. Internal organs and
musculature yellowish to amber; muscle bands evident
where not obscured by squamation.
Etymology.—The specific epithet is a patronym to honor our
good friend and colleague Thomas L. Morris, discoverer and
collector of this new species, renowned cave diver and
speleobiologist, intrepid explorer, and respected conserva-
tionist devoted to the protection of karst habitats and their
associated biotas.
Distribution and habitat.—Caecieleotris morrisi is currently
known from only a single cave system beneath Presa Miguel
Alema
´n reservoir, northern State of Oaxaca, Mexico, located
along the east side of the Sierra Mazateca front range (Fig. 4).
The lake is sometimes also referred to as Temascal, name of
an adjacent municipality (also known as Nuevo Soyaltepec)
and associated hydroelectric plant. This artificial impound-
ment was created following the construction of Presa (¼dam)
Miguel Alema
´n, a large dam on the Tonto River, major
headwater tributary of the R´
ıo Papaloapan draining into the
southwestern Gulf of Mexico. Construction of the dam
began in 1949 and filling of the reservoir was completed in
1955. The 830 m (2,723 ft) long dam and 9,300 km
2
(3,591
mi
2
) reservoir provides hydroelectricity, flood control, and
irrigation supply. The dam is operated in conjunction with
the Cerro do Oro Dam (and associated 220 km
2
,85mi
2
reservoir) located on the Santo Domingo River, which is
joined to Presa Miguel Alema
´n reservoir by a short, narrow
channel. The Tonto and Santo Domingo rivers join to the
south of the city of San Juan Bautista Tuxtepec to form the
R´
ıo Papaloapan, Mexico’s second largest river (mean annual
discharge 3.73310
4
m
3
; Miller et al., 2005).
The cave entrance at the type locality lies at a depth of
about 6.1 m (20 ft) beneath a rocky bluff along the shoreline
Table 2. Measurements and meristic counts of type specimens (n¼11) of Caecieleotris morrisi. Range, mean, and standard deviation (SD) of
measurements include values for the holotype.
Holotype
Range Mean SDCNPE-IBUNAM 19073
Standard length (SL, mm) 34.1 19.3–34.1 27.0 4.9
Percent SL
Head length (HL) 34.4 29.2–42.5 35.6 3.2
Pre anal-fin length 60.1 56.5–67.8 62.4 3.5
Pre spinous-dorsal fin length 45.5 42.7–50.0 46.1 2.0
Pre rayed-dorsal fin length 60.1 58.5–61.9 59.9 1.2
Pre pelvic-fin length 30.8 29.8–33.9 32.1 1.2
Pre pectoral-fin length 29.3 28.8–35.6 31.1 2.1
Pectoral-fin origin to spinous dorsal-fin origin 8.0 7.8–11.8 9.4 1.1
Body depth at pelvic-fin origin 17.6 14.2–18.6 16.4 1.6
Caudal peduncle depth 7.8 7.4–8.4 7.9 0.3
Caudal peduncle length 17.6 17.6–28.4 24.3 3.5
Caudal peduncle width 4.4 2.9–5.4 3.9 0.7
Body width at pectoral-fin origin 13.5 11.6–17.4 14.2 1.9
Pectoral-fin length 42.2 30.8–42.2 34.8 3.3
Pelvic-fin length 21.1 15.0–21.1 17.2 1.9
Anal-fin base length 13.5 11.4–19.8 14.7 2.8
Spinous dorsal-fin base length 9.4 6.7–13.4 9.9 2.0
Rayed dorsal-fin base length 15.0 7.4–18.2 14.7 2.8
Percent HL
Head width 63.4 54.1–68.2 62.7 4.9
Upper jaw length 36.1 27.0–40.9 31.2 4.2
Lower jaw length 37.4 28.1–45.5 33.1 5.0
512 Copeia 104, No. 2, 2016
of the lake. Immediately within the cave, the depth descends
to about 27.4 m (90 ft) before rising to a depth of about 12.2
m (40 ft) where it then levels off. Divers with the collecting
party observed flowstone in the cave (sheet-like mineral
deposits typically composed of calcite). This suggests that
prior to impoundment the entrance might have been a high-
water, wet season overflow, and that a lower (now deeper)
entrance might exist that could have been a perennial
artesian spring in pre-reservoir conditions (Tom Morris, pers.
comm.). In addition to this cave the dive team explored a
submerged sulfur spring nearby where, as expected, no
higher taxa were observed.
Conservation status.—All cavefish species of North America
are in some level of jeopardy due to endemic distributions
and the vulnerability of subterranean habitats to land-use
changes and environmental perturbations (Jelks et al., 2008),
as is the general case with cavefishes globally (Proudlove,
2001, 2006). Higher taxonomic groups (genera and families)
with obligate cave-dwelling species have disproportionately
high levels of imperilment in comparison to groups com-
prised primarily of epigean forms. Stygobitic ictalurids
(Prietella lundbergi,P. phreatophila,Satan eurystomus,and
Trogloglanis pattersoni) are considered endangered, and the
number of at-risk species in other families is high relative to
the total number of taxa in each group or the number
distributed in North America: a single species (Typhliasina
pearsei) of Bythitidae (100%), the Amblyopsidae (6 of 7
species, 86%; although Typhlichthys represents a species
complex according to Niemiller et al., 2012), and the
Heptapteridae (6 of 9, 67%; Jelks et al., 2008; Chakrabarty
et al., 2014). Insofar as C. morrisi is presently known only
from the type series collected over two decades ago and
nothing is known regarding distribution or population
abundance, it is strictly conjecture to speculate about
conservation status of the species. However, there have been
extensive hydrologic modifications in the region of the type
locality, and the biologically rich State of Oaxaca has
undergone extensive land-use changes over the last few
decades. These changes include widespread deforestation
(Vela
´zquez et al., 2003) that is projected to continue into the
future (G´
omez-Mendoza et al., 2006), one of many factors
known to degrade and threaten subterranean habitats
(Bichuette and Trajano, 2010). Within central Mexico many
endemic fishes are considered imperiled (Dzul-Caamal et al.,
2012). Given current and projected land-use conditions, it
may be prudent for the Mexican government to consider
protective status for C. morrisi under the Norma Oficial
Mexicana (NOM; SEMARNAT, 2010), pending further explo-
ration and studies to evaluate population status, distribution,
and ecology of this unique species.
DISCUSSION
The Gobiiformes is diagnosed by at least 14 putative
synapomorphies (Wiley and Johnson, 2010) identified from
among a broad suite of osteological and myological charac-
ters that have been extensively examined by various
investigators in efforts to determine relationships within this
species-rich order as well as to explore possible relationships
of the Gobiiformes with other percomorph groups (e.g.,
Springer, 1983; Hoese and Gill, 1993; Johnson and Brothers,
1993; Winterbottom, 1993; Thacker, 2009; Gill and Mooi,
2012). A comprehensive morphological analysis of C. morrisi
is beyond the scope of the present study. Furthermore,
suboptimal quality of the only cleared-and-stained specimen
(CS; 28.2 mm SL, presumably a juvenile or subadult) and lack
of specimens exhibiting a complete series of ontogenetic
stages precludes a detailed evaluation of many of these
characters. Nevertheless, certain character states observed in
the CS specimen confirm that the new taxon is a gobiiform:
pelvic intercleithral cartilage is present; ventral intercleithral
cartilage is present; hypurals 1 and 2 are fused; hypurals 3
and 4 are fused to each other and to the urostyle; the dorsal-
most pectoral ray articulates with the posterior margin of the
dorsal-most actinost and lacks a medial enlarged articular
base; infraorbital bones consist of paired lacrimals and the
second element is apparently reduced or absent; supraneurals
are absent; and sensory papillae are distributed extensively
on the head and body.
Placement of C. morrisi in the Eleotridae is provisional on
the basis of a limited number of readily observable characters.
Monophyly of the family as currently recognized is ques-
tionable, and the group is generally defined by plesiomor-
phic rather than derived characters (Hoese, 1984; Thacker,
2009). Typically, species of Eleotridae, Butidae, Rhyacich-
thyidae, and Odontobutidae are separated from the Gobiidae
and Gobionellidae in having six (versus five) branchiostegal
rays (Hoese, 1984; Hoese and Gill, 1993; Thacker, 2011; Gill
and Mooi, 2012). Specimens of the type series of C. morrisi
exhibit unusual variation of 4–6 (modally 6) branchiostegals,
with an asymmetrical number on each side in at least one
individual; the small anterior elements are difficult to discern
in alcohol-preserved specimens, but a reduced number may
be related to developmental truncation as a result of extreme
troglomorphy. As in most other eleotrids, C. morrisi also has
separate pelvic fins, unlike the majority of other gobiiforms.
Also, as is characteristic of other eleotrids (Hoese and Gill,
1993), C. morrisi appears to have procurrent cartilages of the
caudal fin elongated posteriorly and extended over the
Fig. 4. Map of Presa Miguel Alema
´n and vicinity, Oaxaca, Mexico, type
locality (vertical arrow) of Caecieleotris morrisi. Source: Wikimedia
Commons (http://en.wikipedia.org/wiki/File:Papaloapanrivermap.
png).
Walsh and Chakrabarty—New cavefish from Mexico 513
anterior epural(s). Unusual variation observed in some
meristic and mensural characters of the type series may be
attributable, in part, to developmental truncation as result of
troglomorphy, contortion of preserved specimens, inaccurate
counts or measurements (difficult given the lack of pigmen-
tation and small body size), or a combination of factors.
The discovery of C. morrisi brings to 13 the number of
described stygobitic gobiiforms worldwide, and to four the
number of Eleotridae, with an additional undescribed cave
sleeper reported from Guam (Table 1). Most notably, C.
morrisi represents the only cave-adapted sleeper known from
Atlantic Ocean drainages, with all others confined to the
Indo-Pacific region. Two of the four described cave sleepers
(Oxyeleotris caeca and O. colasi) occur on the island of New
Guinea and are thought to be related to each other, as well as
to O. fimbriata, an epigean species that is distributed widely
in New Guinea and northern Australia (Allen, 1996). There is
also molecular evidence supporting monophyly of O. colasi
with the epigean O. marmorata (type species of the genus)
and O. lineolata, in a phylogenetic analysis that included
eight other Indo-Pacific and eastern Atlantic gobiiforms
(Pouyaud et al., 2012). Bostrychus microphthalmus is a cave
eleotrid from Sulawesi that appears to be most similar
morphologically to B. sinensis, a wide-ranging tropical Indo-
Pacific species that most commonly occurs in mangroves and
estuaries, and occasionally enters fresh water, along with
other congeners that occur in or are confined to fresh waters
(Hoese and Kottelat, 2005). In the molecular analysis by
Pouyaud et al. (2012), B. sinensis appears as the sister taxon to
the monophyletic Oxyeleotris. Other molecular phylogenetic
studies have demonstrated that cave gudgeons of the genus
Typhleotris (T. madagascariensis,T. mararybe, and T. pauliani),
endemic to karst systems in southwestern Madagascar, are
the sister group to Milyeringa (M. justitia and M. veritas),
endemic to similar cave habitats in northwestern Australia
(Chakrabarty et al., 2012). The phylogenetic position of
Milyeringa within the Gobiiformes has been questioned
(reviewed by Larson et al., 2013), and some authors place
the genus in the Eleotridae (references in Table 1 footnote),
but the nuclear DNA evidence suggests a distinct relationship
with eleotrids and supports recognition of the group at the
family level, Milyeringidae (Tornabene et al., 2013; Thacker
et al., 2015). We should note that attempts to extract and
amplify DNA from specimens of C. morrisi failed, possibly
due to exposure to formalin at some stage of preservation.
The aforementioned cave-adapted species share conver-
gent characters that are common to stygobitic fishes and that
are the subject of extensive study, i.e., loss or reduction of
eyes and pigmentation, hyper-development of non-optic
sensory systems, and other morphological features associated
with a hypogean lifestyle. Among the cave-dwelling eleotrids
and milyeringids there is a gradation of these morphological
characters (see Diagnosis), suggesting that considerable
differences exist between taxa based on divergence times
from ancestral lineages and concomitant time that selective
forces have been acting during cave existence. Indeed, a
remarkable ancient sister-group relationship and the widely
disjunct Malagasy-Australian distribution of the milyeringids
reveals the historical extent to which individual lineages may
be subjected to similar evolutionary processes acting inde-
pendently in the hypogean environment (Chakrabarty et al.,
2012).
The pronounced troglomorphic features of C. morrisi,
namely the near complete loss of eyes, absence of all
pigmentation, and well-developed neuromast/sensory papil-
lae system suggest that this species has an ancient history of
living in darkness. Based on geography alone, it is unlikely
that C. morrisi shares a close relationship with other
described cave gobiiforms. It is most parsimonious to infer
that C. morrisi shares a common ancestral lineage with one or
more species of extant eleotrids in the westcentral Atlantic,
particularly those species ranging in the Gulf of Mexico and
western Caribbean, but gross morphological features do not
provide insight into possible relationships. However, biogeo-
graphical patterns from multiple taxonomic groups provide
evidence of historical linkages between freshwater faunas of
the R´
ıo Papaloapan drainage and the Central American/
Neotropical realm (Huidobro et al., 2006; Quiroz-Martinez et
al., 2014). The R´
ıo Papaloapan is part of the Papaloapan-
Coatzacoalcos division of the Usumacinta ichthyofaunal
province (Miller et al., 2005). Within this major province
fish diversity is great, with over 200 described species, over
half of which are restricted to fresh waters; of those
permanent freshwater species, at least 18 are thought to be
derived from marine ancestors. About one quarter of the R´
ıo
Papaloapan ichthyofauna is endemic, including two species
of cave hepapterids (Rhamdia reddelli and R. zongolicensis).
Moreover, considered in its entirety, the Usumacinta ich-
thyofaunal province is occupied largely by taxa of Middle or
South American derivation (Miller et al., 2005; Matamoros et
al., 2015). Thus, possible phylogenetic affinities of C. morrisi
with taxa outside of the Gulf of Mexico or circum-Caribbean
region cannot be precluded.
Mexico has six extant, epigean eleotrid species in Gulf
Coast drainages: Dormitator maculatus,Eleotris amblyopsis,
Eleotris perniger,Erotelis smaragdus,Gobiomorus dormitor, and
Guavina guavina (Castro-Aquirre et al., 1999; Miller et al.,
2005). An additional five eleotrid species occur on the Pacific
Slope of Mexico: Dormitator latifrons,Eleotris picta,Erotelis
armiger,Gobiomorus maculatus,andGobiomorus polylepis.
Caecieleotris morrisi exhibits a generalized eleotrid shape with
a depressed head and elongate, slightly compressed body,
and perhaps is most similar in shape to species of Eleotris and
Erotelis. However, the very large spatulate-shaped head of C.
morrisi is more typical of some of the other cave gobiiforms
and is especially similar to that of Oxyeleotris (see Allen,
1996:fig. 3; Pouyaud et al., 2012:figs. 2–3), most likely
relating to convergence in these cave obligates. Future study
may not only be informative in determining the phyloge-
netic relationship of C. morrisi with other Atlantic or Pacific
eleotrids, but could provide interesting clues about biogeog-
raphy, as well as placing into an evolutionary context
information gleaned about convergence in morphology and
other aspects of the biology of cave-adapted sleepers.
The discovery of C. morrisi in southcentral Mexico is not
surprising given the number of endemic hypogean species of
other freshwater taxa in the region and the many stygobitic
fishes documented elsewhere in Mexico (Hubbs, 1938) and
karst regions of the eastern and central United States,
Caribbean, and Neotropics (Proudlove, 2006). Central Mex-
ico has a notable subterranean invertebrate fauna, especially
decapod crustaceans that have invaded cave systems inde-
pendently and that are thought to have been derived from
surface or marine ancestors with affinities to cavernicolous
species in the United States, Central America, and the
western Caribbean region (Hobbs et al., 1977; Hobbs, 1994;
Hobbs and Lodge, 2010). Among countries of the world,
Mexico ranks third (behind China and Brazil) in number of
known hypogean fish species, with about 12 valid species
and several additional taxa of unresolved taxonomic status
514 Copeia 104, No. 2, 2016
(e.g., infraspecific populations of Astyanax and Rhamdia).
This number represents approximately 7% of stygobitic
fishes worldwide (Proudlove, 2010). In Mexico, as is the case
globally, most hypogean fishes are ostariophysans. Caecie-
leotris morrisi is thus a unique taxon in representing the only
known obligate cave gobiiform in the Western Hemisphere.
MATERIAL EXAMINED
Comparative material examined included several eleotrid
and gobiid species that occur in the general geographic
region of the new taxon, including westcentral Atlantic and
eastcentral Pacific drainages.
Awaous banana: LSUMZ 14826, 2, Panama, Dari´
en Province,
Puerto La Cantera, 1 April 2011.
Dormitator latifrons: LSUMZ 14555, 1, Honduras, Departa-
mento de Atla
´ntida, E edge of Sambo Creek, 8 January 2011;
UF 15255, 1 CS, Mexico, Colima State, mangrove swamp 1.7
mi SW of Tecoma
´n, 1 June 1966.
Dormitator maculatus: LSUMZ 15901, 35, Honduras, Departa-
mento de Colon, Laguna Guaimoreto, 10 September 2011;
UF 87885, 1 CS, Florida, Martin County, Danforth Creek on
Co Rte 714 about 1 mi E of turnpike, 9 September 1991.
Eleotris amblyopsis: LSUMZ 15635, 2, Honduras, Departamen-
to de Cort´
es, Barra del Motagua, community of Omoa, 8
September 2011; UF 67681, 28 (1 CS), Costa Rica, Lim ´
on
Province, Benjamin Creek 1 mi upstream Tortuguero River,
17 August 1969.
Eleotris perniger: LSUMZ 14540, 8, Honduras, Departamento
de Atla
´ntida, Cureo River mouth, Refugio de Vida Silvestre, 9
January 2011; UF 27603, 34 (2 CS), Panama, Kuna Yala
Province, creek 0.5 mi N of Puerto Obaldia, 4 May 1965.
Erotelis smaragdus civitatum: LSUMZ 4475, 2, Louisiana,
Jefferson Parish, Bay Macoin, 9 July 1973.
Gobiomorus dormitor: LSUMZ 15003, 1, Honduras, Departa-
mento de Colon, Barra Sico, Laguna Bacalar, 28 November
2010; UF 27515, 20 (1 CS), Panama, Canal Zone, Gatun Lake,
Frijoles Landing, 26 April 1965.
Gobiomorus maculatus: UF 19619, 1 CS, Costa Rica, Punta-
renas Province, tidal stream of estuary at Quepos, 2 July
1973.
ACKNOWLEDGMENTS
We are grateful to D. W. Nelson (UMMZ) for aid with loans
and for facilitating collaboration between the authors. C. R.
Gilbert (UF) first recognized and brought to the senior
author’s attention the importance and distinctiveness of this
taxon. Curatorial assistance and loans of specimens were
arranged by R. R. Robins, L. M. Page, and Z. S. Randall (UF)
and C. D. McMahan (LSU). We thank H. Espinosa-Per´
ez
(UNAM) for arranging for permits and depositing the
holotype in Mexico, H. L. Jelks (USGS) for assistance with
photography, and J. J. Schmitter-Soto (ECOSUR) for provid-
ing a Spanish translation of the abstract. Constructive
comments on a draft of the manuscript were provided by
W. F. Loftus. Partial funding for this work was also supplied
by National Science Foundation grant DEB 1354149.
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